10 Infectious Disease Developments That Defined Q2 2026

The second quarter of 2026 delivered a remarkable concentration of regulatory milestones, outbreak events, and pipeline advances across infectious disease. From the first-ever US approval for hepatitis delta virus to landmark HIV treatment options and a cruise ship outbreak that put the country's biopreparedness infrastructure to the test, the April–June period was among the most consequential quarters for the field in recent memory. The Contagion team covered each development as it unfolded. Here is a summary of 10 of the most significant stories from Q2 2026.

1. FDA Approves Doravirine/Islatravir (Idvynso), a First-in-Class 2-Drug HIV Regimen

On April 21, 2026, the FDA approved doravirine/islatravir (Idvynso; Merck) as a single-tablet, once-daily regimen for adults living with HIV who have achieved virologic suppression and have no history of treatment failure or resistance to doravirine. The approval marks the first and only non–integrase strand transfer inhibitor (INSTI), tenofovir-free, complete 2-drug regimen approved for this population.

The approval was supported by phase 3 data from the DRIVE-SWITCH and IMPOWER trials, in which the DOR/ISL combination demonstrated noninferior efficacy to standard 3-drug regimens in maintaining viral suppression. In a 96-week analysis, more than 92% of participants who switched to DOR/ISL maintained viral suppression, with no treatment-emergent resistance to either doravirine or islatravir observed through 2 years of follow-up.

2. Andes Hantavirus Cluster Aboard MV Hondius Cruise Ship: Outbreak, Repatriation, and Clinical Response

What began as a report of unusual respiratory illness among passengers aboard the MV Hondius in the South Atlantic became the most-followed infectious disease outbreak story of Q2 2026. By early May, 11 passengers had been infected with the Andes species of hantavirus — the only hantavirus strain known for limited human-to-person transmission via respiratory droplets — with illness onset occurring between April 6 and 28. Three patients died; others progressed to acute respiratory distress syndrome and shock.

The US Department of Health and Human Services coordinated the medical repatriation of 17 American citizens to the United States, with 2 transported in onboard biocontainment units. Patients were housed at the University of Nebraska Medical Center's biocontainment unit.

3. Bulevirtide-gmod (Hepcludex) Becomes First FDA-Approved Treatment for Chronic Hepatitis Delta Virus

On May 22, 2026, the FDA approved bulevirtide-gmod (Hepcludex; Gilead Sciences) injection under its Accelerated Approval pathway, closing a therapeutic void that has persisted since HDV was first identified. The approval covers adults without cirrhosis or with compensated cirrhosis and was supported by Priority Review, Breakthrough Therapy Designation, and Orphan Drug Designation.

HDV requires coinfection with hepatitis B virus to replicate, affecting an estimated 5% of the more than 300 million people living with chronic HBV globally. The FDA labeling for bulevirtide-gmod carries a boxed warning: discontinuation of therapy may result in severe acute exacerbations of both HDV and HBV infection. Clinicians should ensure post-treatment monitoring protocols are in place and counsel patients accordingly before initiating therapy.

"Today's approval fills a critical gap in care for patients with chronic HDV infection, who until now have had no FDA-approved therapies available," said Wendy Carter, DO, Acting Director of the Office of Infectious Diseases in FDA's Center for Drug Evaluation and Research.

4. Bepirovirsen Phase 3 Data Signal a Potential Functional Cure for Chronic Hepatitis B

Results from the pivotal B-Well 1 and B-Well 2 phase 3 trials demonstrated that bepirovirsen (GSK/Ionis Pharmaceuticals), an antisense oligonucleotide targeting all HBV messenger RNAs, achieved functional cure in approximately 20% of patients with chronic hepatitis B virus infection. The trials enrolled more than 1,800 patients across 29 countries.

Functional cure was defined as HBV DNA below the lower limit of quantification and hepatitis B surface antigen (HBsAg) below 0.05 IU/mL for at least 24 weeks after completing treatment. Unlike nucleos(t)ide analogs, which suppress viral replication without eliminating the virus, bepirovirsen is designed to enable durable off-treatment response. GSK has indicated it anticipates its first regulatory decision in Q3 2026; ongoing 96-week follow-up data will be critical for assessing durability and potential label expansion.

5. FDA Approves Tebipenem Pivoxil (Utebzi) as First Oral Carbapenem for Complicated Urinary Tract Infections

The FDA approved tebipenem pivoxil hydrobromide (Utebzi; Spero Therapeutics/GSK) for the treatment of complicated urinary tract infections, including pyelonephritis, in adults, making tebipenem the first oral carbapenem antibiotic available in the US. The approval was supported by results from the phase 3 PIVOT-PO trial (NCT06059846), which was stopped early for efficacy. In the modified intention-to-treat population, tebipenem HBr achieved an overall success rate of 58.5% (261/446 participants) compared with 60.2% (291/483 participants) for IV imipenem-cilastatin, with an adjusted treatment difference of −1.3% (95% CI, −7.5 to 4.8%), meeting the prespecified noninferiority margin.

6. FDA Approves Ensitrelvir (Xocova) as First Oral Antiviral for Postexposure Prevention of COVID-19

The FDA approved ensitrelvir (Xocova; Shionogi) for the prevention of COVID-19 in adults and children 12 years and older following exposure to a person with confirmed COVID-19, making it the first and only oral antiviral authorized in the US to help prevent symptomatic infection after exposure. The approval was supported by results from the SCORPIO-PEP phase 3 trial, published in the New England Journal of Medicine in May 2026. The trial enrolled 2,387 participants aged 12 or older; in the primary mITT analysis (n = 2,041), a 5-day course of ensitrelvir initiated within 72 hours of exposure reduced the risk of COVID-19 by 67% compared with placebo through day 10 (P < .001).

7. Ebola Outbreak in the DRC and the US Biopreparedness Question

As the WHO declared the Bundibugyo ebola virus outbreak a public health emergency in the Democratic Republic of Congo, Contagion examined what concurrent federal funding and personnel cuts to high-consequence infectious disease programs mean for the country's ability to respond. Jason Goldman, MD, MACP, addressed whether existing protocols, infrastructure, and personnel remain adequate despite the reductions. The CDC reported 321 confirmed cases in the DRC outbreak as of late June.

8. FDA Approves Cefepime/Zidebactam (Zaynich) for Complicated UTIs Including MDR Gram-Negative Pathogens

In May, the FDA approved cefepime/zidebactam (Zaynich) for the treatment of complicated UTIs and pyelonephritis in adults, providing a new therapeutic option for multidrug-resistant gram-negative organisms including carbapenem-resistant pathogens. The combination pairs cefepime, a fourth-generation cephalosporin, with zidebactam, a novel bicyclic boronic acid beta-lactam enhancer with dual mechanism of action. Together with tebipenem's approval in the same month, Q2 2026 delivered two new first-in-class or novel-mechanism options for drug-resistant UTI in rapid succession — a meaningful development for ID pharmacists and clinicians managing complicated UTI in patients with resistant gram-negative infections or limited IV access.

9. FDA Accepts Priority Review for Gilead's BIC/LEN Single-Tablet HIV Regimen; Decision Expected August 27

The FDA accepted Gilead Sciences' New Drug Application for bictegravir 75 mg/lenacapavir 50 mg (BIC/LEN) and granted Priority Review, with a PDUFA date of August 27, 2026. The investigational once-daily, single-tablet regimen is designed for adults living with HIV who are already virologically suppressed, combining bictegravir — an integrase inhibitor with a high barrier to resistance — with lenacapavir, a first-in-class capsid inhibitor with a novel mechanism of action carrying no cross-resistance to existing antiretrovirals. If approved, BIC/LEN would become the first single-tablet regimen to pair an integrase inhibitor with a capsid inhibitor.

10. mRNA-based Influenza Vaccine Advances Against HHS Resistance

An FDA advisory committee voted unanimously (9-0) on June 18 to find the mRNA-based investigational seasonal influenza vaccine mRNA-1010 (Moderna) safe and efficacious, with benefit outweighing risk in preventing influenza in adults 50 years and older.

The finding by the Vaccines and Related Biological Products Advisory Committee (VRBPAC) does not obligate the FDA to approve the product, but it is required to take action on the application by August 5 to comply with the Prescription Drug User Fee Act (PDUFA).

References

1. Contagion Editorial Team. FDA Approves Doravirine/Islatravir, a First-in-Class 2-Drug HIV Regimen. Contagion. April 21, 2026. Accessed July 3, 2026.

2. Contagion Editorial Team. US Coordinates Medical Repatriation of Passengers from Cruise Ship Hantavirus Exposure. Contagion. May 11, 2026. Accessed July 3, 2026.

3. Hoffman M. Bulevirtide Approved as First US Treatment for Chronic Hepatitis Delta Virus. Contagion. May 22, 2026. Accessed July 3, 2026.

4. Bender K. Bepirovirsen Phase 3 Results Offer Potential Cure for Chronic Hepatitis B. Contagion. June 17, 2026. Accessed July 3, 2026.

5. Fitch J, Saylor B. FDA Approves Tebipenem Pivoxil as First Oral Carbapenem for Complicated Urinary Tract Infections. Contagion. June 18, 2026. Accessed July 3 2026.

6. Contagion Editorial Team. FDA Approves Ensitrelvir as First Oral Post-Exposure Prevention Option for COVID-19. Contagion. June 1, 2026. Accessed July 3, 2026.

7. Parkinson J, Goldman J. Reductions in Funding, Personnel Will Leave US Less Prepared for Future Infectious Disease Outbreaks. Contagion. June 14, 2026. Accessed July 3, 2026.

8. O’Donnell J. Review of Cefepime and Zidebactam, a Novel Antibiotic Approved to Treat Complicated Urinary Tract Infections. Contagion. June 20, 2026. July 3, 2026.

9. Contagion Editorial Team. FDA Will Review Gilead's HIV BIC/LEN Combination. Contagion. April 29, 2026.

10. Bender K. mRNA-based Influenza Vaccine Advances Against HHS Resistance. Contagion. June 22, 2026. Accessed July 3, 2026.